1. Technical Field
The present invention relates in general to volume groups and in particular to volume groups on storage area networks (SAN). Still more particularly, the present invention relates to providing efficient base operating system (BOS) installation for a volume group of a SAN.
2. Description of the Related Art
Management of a computer system's physical memory, including distributed memory, involves dividing the physical memory into manageable sections, assigning physical addresses to those sections, and mapping those physical addresses to logical addresses. In some currently available computer systems, the management of the physical memory includes combining direct access storage devices (DASD) (also referred to as hard disks or physical volume (PV)) into groups called volume groups. Within each volume group, one or more logical volumes (LVs) are defined, which may be utilized for a number of system purposes, such as paging, storing raw data, or hosting a single file system.
Software known as logical volume managers (LVM), or simply volume managers, manages the fixed disk storage and the volume groups. The volume manager combines storage space on one or more hard disks into a single volume group and links the computer system's kernel to the volume group.
One example of a conventional LVM is the AIX LVM, which supports two volume group types: one with 32 disks and 256 logical volumes and one with 128 disks and 512 logical volumes, although further improvements are being made to accommodate larger numbers of disks and logical volumes. A volume manager such as AIX LVM provides virtualization between the physical disks and the user of the disk space such as a file system.
Each logical volume consists of one or more logical partitions (LPs), each corresponding to at least one physical partition, which is a fixed size region of space on a disk. If mirroring is specified for the logical volume, additional physical partitions are allocated to store the additional copies of each logical partition. These virtual logical disk devices appear to applications, databases, and file systems as if they where a physical disk device. However, a logical volume does not have the physical limitations of physical disk devices, and because of its virtual nature, a logical volume is not restricted to particular disks or a specific area of a disk. Data in logical volumes appears to be contiguous to the user but can be discontinuous on the physical volumes. This allows file systems, paging space, and other logical volumes to be re-sized or relocated, span multiple physical volumes, and have their contents replicated for greater flexibility and availability in the storage of data.
Because LVM is able to create logical volumes that appear contiguous in user space but which that map to discontinuous spaces on disks, the disks are not required to be physically located within the system executing the LVM. In fact, the disks are often located remote from the computer system on which the LVM is executing and accessed via a network. The LVM then enables a system administrator to activate a particular logical volume for use by the client systems. For example, a file system is hosted on a logical volume, and once the boot process completes, the file systems is available to be mounted by remote client systems via the network.
One network type that has combined the functionality of having multiple disk storage distributed across a network utilized for hosting file systems (and other applications) is a storage area network (SAN). Storage area networks are becoming more common in the computer network arena. A SAN comprises a network of storage disks that operate as a single resource and often links multiple servers together that each access the storage disks. An additional functionality of the SAN is that it enables data transfers between computers and disks at the same high peripheral channel speeds as when the two sets of components are coupled directly to each other. Thus, unlike conventional network file systems, which support client access to a file system over the Internet via transmission control protocol/Internet Protocol (TCP/IP), a SAN's file system appears as a directly connected storage device to the client, and the file system stored on a SAN is accessible without IP support. Also, although the storage disks may be located at different locations, a SAN allows the system administrator to access the various disks from a single boot location.
Access to and operation of a file system and logical volume requires a boot device that activates the SAN. Further, the logical volumes each have a boot image as well as images of other files, etc. that are to be installed in a file system. The boot installation of devices within a SAN may be completed via several different techniques. In one conventional method, a CD ROM is provided with a boot image having a base operating system (BOS). This method is limited to a single medium (typically 700 MB) or several similar media stacked together.
Currently, a boot device is identified in a nonvolatile random access memory (NVRAM), such as a CD or hard disk. Therefore, if a maintenance operation or installation requires the computer to boot from an alternative device, the identified device must be changed in NVRAM. For example, if an install operation is to be performed on a computer, an administrator may need to boot the computer from a removable medium, such as a compact disk (CD). Therefore, the administrator changes the boot disk in the computer to refer to a CD drive on the SAN.
In some conventional networks, a network install manager (NIM) is utilized to provide a network boot. With NIM, a first networked machine (server) requests the boot image from another server and installs individual pieces of software/products from the other server. Also, with NIM and with network file system (NFS), mounts installation/reading of the boot logical volume (bootlv) and installation of images in other networks occur at Internet Protocol (IP) speeds. This boot process requires the boot images and optional programming product OPP images be transmitted across the Internet in order to be installed and therefore incurred significant amounts of latency. Further, whenever the network is experiencing a down-time (i.e., network unavailable), NIM does not function and features such as disaster recovery cannot easily be accomplished.
Given the limitations of current implementations, which provide the boot image on a single removable CD that is also utilized to enable mounting of the file system, the present invention recognizes that it would be desirable to create a volume group with a boot Device that is more easily accessible than via NIM installation across an IP network. The invention further realizes that it would be beneficial to provide the boot device within the SAN and remove reliance from external devices that may not be accessible when required. These and other benefits are provided by the invention described herein.